(819c) Free Surface Electrospinning of Aqueous Polymer Solutions From a Wire Electrode

Authors: 
Rutledge, G. C., Massachusetts Institute of Technology


FREE SURFACE ELECTROSPINNING OF AQUEOUS POLYMER SOLUTIONS FROM A WIRE ELECTRODE

Indrani Bhattacharyya, Gregory C. Rutledge

Massachusetts Institute of Technology, Cambridge, MA 02139

            In recent years, electrospinning has proven to be an extremely promising technique, enabling researchers to create excellent materials for various applications, such as filtration, drug delivery, textiles, nanocomposites and tissue engineering. In the conventional electrospinning process, generally, a needle or a nozzle is used as the spinneret. A typical production rate for such a set-up being rather low (~0.1-1 g of fiber/hour), it has been difficult to employ this process in industrial settings. To overcome this issue, several “needleless” or “free surface” electrospinning techniques have been investigated over the past few years, in which multiple jetting is promoted simultaneously from a sufficiently large area of liquid surface. One such technique involves jetting from the liquid droplets that form on a wire electrode as it exits a bath of liquid with an entrained liquid coating.1 This technique was demonstrated for a solution of polyvinyl pyrrolidone (PVP) in ethanol, and a model was proposed to describe its productivity. Here, we extend this analysis to different polymer solutions, with particular emphasis on aqueous solutions, and modify the model as necessary to account for the observed productivity for a variety of polymer solutions.

            Besides being the most desirable solvent for industrial use due to its negligible recycling cost, water is of particular importance in the pharmaceutical and food processing industries. However, water-based polymer solutions are difficult to electrospin from the wire electrode due to their high surface tensions and often high viscosities, even at relatively low polymer concentrations. For this study, three different water-soluble polymers are chosen e.g., polyethylene oxide (PEO), polyvinyl alcohol (PVA) and hydroxypropyl methyl cellulose (HPMC), which are widely used in both pharmaceutical and food industries. We address a few particular challenges encountered with these solutions, such as thin film formation between the wires on the rotating wire spindle and jetting of highly viscous liquids, with a simple modification of the existing spindle design. Some newly observed features, such as the formation of satellite droplets on the wire electrode and incomplete jetting from the droplets, are discussed.

Reference

1.         Forward, K. M.; Rutledge, G. C., Free surface electrospinning from a wire electrode. Chemical Engineering Journal 2012, 183, 492-503.